Electrical photosemiconducting and paramagnetic properties of polypyromellitimides

Semiconducting properties with dark and photoconductivity, type r, were observed in polypyromellitimides (PPMI) and explained by a donor-acceptor interreaction in the PPMI between electron acceptor promellitimide fragments and electron donor diamide in adjacent macromolecules

Semiconducting properties of Cu5SbO6

Thermoelectric power, electrical resistivity, I V characteristics, relative electrical permittivity, dc magnetization and ac magnetic susceptibility measurements carried out on Cu5SbO6 showed p-type semiconducting behaviour with the activation energy of 0.24 eV as well as ferrimagnetic order with the Néel temperature of 5.2 K. The e ective magnetic moment of 5.857 B/f.u. revealed the orbital contribution to the magnetic moment. Large value of the relative electrical permittivity indicated that the Cu2+ ions with the unscreened and un lled electron shells are responsible for the polarizability and forming of electric dipoles

p-Type semiconducting properties in lithium-doped MgO single crystals

The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole) resulting from oxidation was monitored by optical absorption measurements. Both dc and ac experiments provide consistent values for the bulk resistance. The electricalconductivity of oxidized MgO:Li crystals increases linearly with the concentration of ([Li]^{0}) centers. The conductivity is thermally activated with an activation energy of (0.70 +/- 0.01) eV, which is independent of the ([Li]^{0}) content. The \textit{standard semiconducting} mechanism satisfactorily explains these results. Free holes are the main contribution to band conduction as they are trapped at or released from the ([Li]^{0})-acceptor centers. In as-grown MgO:Li crystals, electrical current increases dramatically with time due to the formation of ([Li]^{0}) centers. The activation energy values between 1.3 and 0.7 eV are likely a combination of the activation energy for the creation of ([Li]^{0}) centers and the activation energy of ionization of these centers. Destruction of ([Li]^{0}) centers can be induced in oxidized crystals by application of an electric field due to Joule heating up to temperatures at which ([Li]^{0}) centers are not stable.Comment: LaTeX, 20 pages, 9 Encapsulated Postscript Format Figures, use the version 4.0 of REVTEX 4 macro packag

Length-dependent resistance model for a single-wall Carbon nanotube

The non-linear length-dependent resistance, $\mathcal{R}(l)$ observed in single-wall Carbon nanotubes (SNTs) is explained through the recently proposed ionization energy ($E_I$) based Fermi-Dirac statistics ($i$FDS). The length here corresponds to the Carbon atoms number ($\mathcal{N}$) along the SNT. It is also shown that $\mathcal{R}_y(l_y)$ $<$ $\mathcal{R}_x(l_x)$ is associated with $E_I^y$ $<$ $E_I^x$, which can be attributed to different semiconducting properties in their respective $y$ and $x$ directions.Comment: Publishe

Investigating laser induced phase engineering in MoS2 transistors

Phase engineering of MoS2 transistors has recently been demonstrated and has led to record low contact resistances. The phase patterning of MoS2 flakes with laser radiation has also been realized via spectroscopic methods, which invites the potential of controlling the metallic and semiconducting phases of MoS2 transistors by simple light exposure. Nevertheless, the fabrication and demonstration of laser patterned MoS2 devices starting from the metallic polymorph has not been demonstrated yet. Here, we study the effects of laser radiation on 1T/1T'-MoS2 transistors with the prospect of driving an in-situ phase transition to the 2H-polymorph through light exposure. We find that although the Raman peaks of 2H-MoS2 become more prominent and the ones from the 1T/1T' phase fade after the laser exposure, the semiconducting properties of the laser patterned devices are not fully restored and the laser treatment ultimately leads to degradation of the transport channel

Some semiconducting properties of Barium Titanate

A number of single crystals of barium titanate have been grown by the flux melt process. These have been rendered semiconducting by reduction in hydrogen at 800 C for times up to 15 min. The resistivity, Seebeck coefficient and optical absorption coefficient have been measured in these crystals to obtain information about the conduction processes. The temperature of the tetragonal to cubic transition in the reduced crystals has been measured and is shown to be consistent with the results of the resistivity and Seebeck data. The results obtained are consistent with the theory that electrical conduction in these crystals is in the small polaron hopping mode with a drift mobility at room temperature of about 4 X 10(^-4)cm(^2)/V.s. with polaron concentrations reaching a peak of 4.18 X 10(^20)cm(^-3).The variation of polaron concentration with reduction time is similar to that obtained by Arend et al. by chemical analyses